Military

Further Reading

CHAPTER 2

M60 MACHINE GUN

The 7.62-mm M60 machine gun supports the rifleman in offense and defense. It provides the heavy volume of close and continuous fire the rifleman needs to accomplish his mission. The M60 is used to engage targets beyond the range of individual weapons, with controlled and accurate fire. The long-range, close defensive, and final protective fires delivered by the M60 form an integral part of a unit's defensive fires. This chapter describes the weapon and the types of ammunition it uses in detail and provides a table of general data.

This section describes the M60 machine gun and its components and purposes, ammunition, and blank firing adapters, and how to install them. The primary use of the M60 is to support the rifleman in both offense and defense. It provides the heavy volume of close and continuous fire he needs to accomplish the mission. It can engage targets beyond the capability of individual weapons with controlled, accurate bursts.

The M60 is a gas-operated, air-cooled, belt-fed, automatic machine gun that fires from the open-bolt position (Figure 2-1). It has a maximum rate of fire of 550 rounds per minute. Ammunition is fed into the weapon from a 100-round bandoleer containing a disintegrating metallic split-link belt. It can be fired from the shoulder, hip, or underarm position; from the bipod-steadied position; or from the tripod-mounted position. (See Table 2-1, for general data.)

DANGER

DO NOT INTERCHANGE THE BARREL ASSEMBLY OR THE BOLT ASSEMBLY FROM ONE WEAPON TO ANOTHER. IF YOU DO SO, IT MAY RESULT IN DEATH OR INJURY.

The major components of the M60 and their purposes are shown in Table 2-2 and Figures 2-2 and 2-3. The sights and safety lever are discussed in paragraphs a and b and shown in Figures 2-4 and 2-5.

COMPONENTS

PURPOSES

(1)

Stock assembly

Provides a shoulder support for aiming and firing the M60 machine gun. The stock assembly has a shoulder rest.

(2)

Buffer assembly

Absorbs recoil from the bolt and operating rod assembly at the end of the recoil movement.

(3)

Bolt assembly

Feeds, chambers, fires, and extracts, using the propellant gases and recoil spring for power. It houses the firing pin.

(4)

Operating rod assembly

Transfers power from propelling gases to the bolt and slide assemblies.

(5)

Cover, hanger, and feed assembly

Feeds linked-belt ammunition. Holds the cartridges in position for stripping, feeding, and chambering.

(6)

Barrel assembly

Houses cartridges for firing, directs projectiles, supports fixed front sight, and provides passageway for operating gases. The bipod supports the M60 in the prone position. The telescopic legs can be adjusted to three different lengths.

(7)

Trigger assembly

Controls the firing of the weapon.

(8)

Forearm assembly

Provides thermal insulation to protect the gunner's hands from heat. Has a slotted top to allow air to circulate around the barrel for cooling purposes.

(9)

Receiver assembly

Supports all assembly major components and houses the action of the weapon.

(10)

Rear sight assembly

Adjustable for both windage and elevation allowing the gunner to make changes rapidly.

(11)

Cocking handle assembly

Pulls the moving parts rearward. Moves in a guide rail fixed to the right side of the receiver.

(12)

Tripod (M122) assembly

Together with the tripod, T&E mechanism, and pintle, provides a stable mount and permits a higher degree of accuracy and control.

Table 2-2. Components and purposes.

Figure 2-2. M60 components and tripod.

a. Sights. The front sight is attached to the barrel. The rear sight is mounted on a spring-type dovetail base, and it can be folded down when the gun is moved (See Figure 2-1).

b. Safety Lever. The safety lever is on the left side of the trigger group (Figure 2-1). It has an "S" and an "F" position. On the "S" position, the bolt cannot be pulled to the rear or released to go forward.

WARNING

Manually return the cocking handle to its forward position each time the bolt is pulled to the rear to prevent damage to the cocking and injury to the gunner.

The M60 machine gun uses several different types of 7.62-mm standard military ammunition. The specific type ammunition and its characteristics are shown in Figure 2-3. Soldiers must use only authorized ammunition that is manufactured to US and NATO specifications. The ammunition is issued in a disintegrating, metallic, split-linked belt (Figure 2-4).

(1) Cartridge, 7.62-mm Ball M80. This cartridge is used against light materials and personnel, and for range training.

(2) Cartridge, 7.62-mm Armor-Piercing M61. This cartridge is used against lightly armored targets.

(3) Cartridge, 7.62-mm Tracer M62. This cartridge is used for observation of fire, incendiary effects, signaling, and for training. When tracer rounds are fired, they are mixed with ball ammunition for a mix of four ball rounds to one tracer round.

(4) Cartridge, 7.62-mm Dummy M63. This cartridge is used during mechanical training.

(5) Cartridge, 7.62-mm Blank M82. This cartridge is used during training when simulated live fire is desired. A blank firing attachment is used to fire this ammunition.

b. Storage. The ammunition is stored under cover. If ammunition is in the open, it must be kept at least 6 inches above the ground and covered with a double thickness of tarpaulin. The cover must be placed so that it protects the ammunition yet allows ventilation. Trenches are dug to divert water from flowing under the ammunition.

c. Care, Handling, and Preservation. Ammunition should not be removed from the airtight containers until ready for use. Ammunition removed from the airtight containers, especially in damp climates, may corrode.

(1) Ammunition must be protected from mud, dirt, and moisture. If ammunition gets wet or dirty, it must be wiped off before use. Lightly corroded cartridges are wiped off as soon as the corrosion is discovered. Heavily corroded, dented, or loose projectiles should not be fired.

(2) Ammunition must be protected from the direct rays of the sun. Excessive pressure from the heat may cause premature detonation.

(3) Oil should never be used on ammunition. Oil collects dust and other abrasives that may possibly damage the operating parts of the weapon.

d. Packaging. The ammunition box contains two cartons. Each carton has a bandoleer for carrying purposes. Each carton contains 100 rounds and weighs about 7 pounds. Ammunition in the bandoleers may be linked together, attached to the hanger assembly, and fired from the container; or, the bandoleers may be removed for firing.

The M13 BFA is used on the M60 machine gun when blank cartridges are fired to simulate live firing during training where live firing is not practical. An M13A1 BFA is also available for the M60 machine gun. The difference between the M13 and the M13A1 is that, on the M13A1, the restrictor tube can be tightened (using a flat tip screwdriver) for a more secure fit, to prevent gas leakage.

DANGER

DO NOT FIRE BLANK AMMUNITION AT ANY PERSON WITHIN 20 FEET. FRAGMENTS OF A CLOSURE WAD OR PARTICLES OF UNBURNED PROPELLANT CAN CAUSE DEATH OR INJURY.

a. Installation of the M13. The BFA must be adjusted to fit the machine gun barrel. The orifice tube fits inside the flash suppressor, flush against the muzzle and flush with the forward end of the flash suppressor. The BFA is clamped tightly to the front sight (Figure 2-5). When properly adjusted, it will fit snugly against the muzzle, thus preventing the escape of gas during firing. When the BFA is manufactured, the distance the orifice tube screws into the restrictor bushing is fixed and fitted by staking the restrictor bushing. This fixed distance, set in the restrictor bushing, does not provide the correct adjustment for every machine gun, because the distance from the muzzle to the forward end of the flash suppressor varies from weapon to weapon. In some instances, the stake mark must be broken, the orifice tube adjusted to fit the barrel, and "restaked."

Figure 2-5. M13 blank firing attachment.

b. Installation of the M13A1. The M13A1 is installed by (Figure 2-6) loosening the lock nut, turning the restrictor tube out a few turns, and loosening the wing nut a few turns. The restrictor tube is inserted in the flash suppressor as far as possible and is clamped around the front sight. The wing nut is tightened finger tight. The restrictor tube is screwed in until it seats tightly against the muzzle end of the barrel to prevent gas leakage, and then the lock nut is tightened.

Figure 2-6. M13A1 blank firing attachment.

c. Care of the M60 While Using the BFA. A buildup of carbon inside the weapon causes friction between the moving parts. Carbon deposits build rapidly when blanks are fired. Stoppages occur when these deposits become excessive. Therefore, the weapon must be kept clean, especially the gas system and chamber, during blank firing. To obtain the best performance when using the BFA, the gunner performs the following:

Proper maintenance contributes to weapon effectiveness as well as unit readiness. Maintenance aspects of the M60 include inspection; cleaning and lubrication; and maintenance before, during, and after firing, and during NBC conditions. Associated tasks essential to maintenance (clearing, general assembly and disassembly, and function checks) are discussed in detail.

The first step in maintenance is to clear the weapon. This applies in all situations, not just after firing. The gunner must always assume the M60 is loaded. To clear the M60, the gunner performs the following procedures. (Subparagraph letters are keyed to the lettered callouts in Figure 2-7.)

a. Moves the safety lever to the "F" position.

b. With his right hand, palm up, pulls the cocking handle in the rear. Moves the safety lever to the "S" position. Returns and locks the cocking handle in the forward position.

c. Raises the cover and conducts the four-point safety check for brass, links, or ammunition.

(1) Checks the feed pawl assembly under the cover.

(2) Checks the feed tray.

(3) Lifts the feed tray and hanger assembly and inspects the chamber.

(4) Checks the space between the face of the bolt and the chamber.

d. Closes the cover and moves the safety lever to the "F" position. Pulls the cocking handle to the rear position. Pulls the trigger and at the same time eases the bolt forward by manually riding the cocking handle forward.

e. Places the safety lever on "S" and raises the cover. (If not disassembling the gun, keep the cover down.)

Figure 2-7. Clearing procedures.

CAUTION

Manually return the cocking handle to the forward and locked position each time the bolt is manually pulled to the rear, or it could cause damage to the weapon.

The gunner performs general disassembly, which is removing and replacing the eight major groups (Figure 2-8). (The unit armorer performs the detailed disassembly. Disassembly beyond this point is prohibited except by ordnance personnel.) During general disassembly, the gunner clears the weapon and places each part on a clean flat surface such as a table or mat. This aids in assembly in reverse order and avoids the loss of parts.

DANGER

BE SURE THE BOLT IS IN THE FORWARD POSITION BEFORE DISASSEMBLY. THE SPRING GUIDE CAN CAUSE DEATH OR INJURY IF THE OPERATING ROD SPRING IS RETRACTED WITH THE BOLT PULLED TO THE REAR.

Figure 2-8. Eight major assemblies.

a. Removing the Stock Assembly. First, the gunner makes sure the bolt is in the forward position. To remove the stock, he raises the shoulder rest, inserts a cleaning rod into the hole to release the latch. He pulls the shoulder stock from the receiver, turns the latch lever, and opens the cover (Figure 2-9).

Figure 2-9. Removal of the stock.

b. Removing the Buffer, Operating Rod, and Bolt Assemblies.

(1) To remove the buffer assembly, the gunner applies slight palm pressure to the rear of the hydraulic buffer assembly. He reaches inside the receiver and pulls up and out on the yoke to remove it from the receiver. He reaches in the back of the receiver and pulls the guide rod and drive spring out the rear of the receiver.(Figure 2-10).

WARNING

The bolt assembly is under spring tension; it can twist and injure your hand.

(2) The gunner removes the operating rod assembly and bolt assembly as a unit. He reaches in the top of the receiver, places a finger on the face of the bolt, and pushes rearward until the bolt and operating rod assemblies extend past the rear of the receiver. Then, he pulls them out as a unit. To separate the bolt from the operating rod, he places the operating rod in his left hand and, with his right hand, pulls the bolt down and away.

CAUTION

Do not use the tip of the driving spring guide assembly as a tool because it could damage the weapon.

d. Removing the Barrel Assembly. The gunner pushes in the spring detent, raises the barrel lock, and removes the barrel assembly(Figure 2-12).

Figure 2-12. Removal of the barrel assembly.

e. Removing the Trigger Mechanism Grip Assembly. The gunner pushes in and removes the flat leaf spring. He pushes out the front pin and slides the trigger mechanism grip assembly slightly forward, then pulls it out to remove it (Figure 2-13).

Figure 2-13. Removal of the trigger mechanism grip assembly.

f. Removing the Forearm Assembly. The gunner inserts a cleaning rod or the reamer portion of a combination wrench through the round opening in the forearm assembly, and then he pushes down on the spring. He lifts and gently slides the forearm assembly from the receiver (Figure 2-14).

CAUTION

Be careful not to damage the internal ribs of the forearm assembly. It can cause damage to the weapon.

Figure 2-14. Removal of the forearm assembly.

g. Removing the Receiver Assembly. Once the forearm assembly is removed, the part remaining is the receiver assembly, and general disassembly is complete.

Inspection begins with the weapon disassembled in its major groups. Shiny surfaces do not mean the parts are unserviceable. The gunner inspects each area of the weapon and related equipment for the conditions indicated. Any broken or missing parts should be repaired or replaced IAW TM 9-1005-224-10. The gunner should perform Preventive maintenance checks and services (PMCS) every 90 days. If the weapon has not been used in 90 days, the PMCS in the operator's manual should be performed regardless. If he sees rust on a weapon, he should perform PMCS immediately.

a. Stock Assembly. The stock assembly should not be cracked and must fit securely on the receiver assembly. The shoulder rest and latch lever should function correctly.

b. Buffer Assembly. The buffer yoke and recess should not be burred, cracked, or bent. The buffer plunger must fit easily into the recess in the spring guide.

c. Operating Rod Assembly. The operating rod, yoke, sear notch, and pins should not have burrs, cracks, or chips. The roller should operate freely. The driving spring should have tension and should not have kinks, breaks, or wear. The guide assembly stop should be tight. If it is loose, the gunner notifies unit maintenance.

d. Bolt Assembly. The bolt assembly is checked for burrs or cracks, especially in the locking lug area.

(1) The roller should operate freely and not be cracked.

(2) The spring should not be kinked.

(3) The threads on the bolt plug assembly and in the breech bolt should not be damaged.

e. Cover Assembly. The cover assembly is checked for burrs, cracks, looseness, or missing parts. The spring action of the front and rear cartridge guides, feed pawls (beneath the cartridge guides), and feed cam assembly are checked. The feed cam assembly should be secure and operate freely.

f. Hanger and Cartridge Feed Tray Assembly. The hanger and cartridge feed tray assembly is checked for burrs, cracks, and missing or loose parts. The feed tray is checked to make sure it fits on the receiver and that the cartridge-retaining pawl works properly. The hanger is checked for obstructions.

g. Barrel Assembly. The barrel assembly is checked for burrs, cracks, and wear, especially in the barrel socket area. The sight and flash suppressor are checked to make sure they are tight. The bipod should work properly, the legs should be straight, and connections should be tight. The bipod plungers should operate smoothly.

h. Trigger Mechanism Grip Assembly. The sear is checked for chips, cracks, or signs of wear. The sear plunger and spring are checked for wear.

i. Forearm Assembly. The forearm assembly is checked for damage.

j. Receiver Assembly. The receiver rails are checked for burrs and wear. The cocking handle should move freely.

k. M122 Mount. The T&E mechanism should not bind. The numbers on the scales and dials must be legible.

(1) Distinct clicks must be heard when the handwheels are turned. Index lines should be calibrated with the indicator pointer.

(2) The pintle should fit snugly in the pintle bushing, and the pintle lock should hold the pintle securely.

(3) The sleeve latch should function properly, and the traversing bar should be tight when the tripod legs are extended and latched.

l. Carrying Case. Maintenance tools and equipment should be complete and serviceable. The case should be serviceable. Frequent washing of the case should be avoided. Such washing may destroy the waterproofing and shrink the case.

The M60 machine gun should be cleaned immediately after firing. The gunner disassembles the M60 into its major groups for cleaning. All metal components and surfaces that have been exposed to powder fouling should be cleaned using CLP on a bore-cleaning patch. The CLP is used on the bristles of the receiver brush to clean the receiver. After the M60 is cleaned and wiped dry, a thin coat of CLP is rubbed on with a cloth. This lubricates and preserves the exposed metal parts during all normal temperature ranges.

CAUTION

Do not get CLP in the gas cylinder when cleaning the barrel. Turn the barrel upside down so that the gas cylinder is above the barrel during cleaning.

a. The gas cylinder components are removed and cleaned only when inspection shows that the piston will not move within the cylinder when the barrel is tilted end-for-end. Unit maintenance personnel must supervise disassembly of the gas system. The receiver brush and swab-holding section of the cleaning rod may be used to clean the interior of the gas cylinder. When CLP is used, the gas cylinder and gas piston must be wiped dry before assembly. After assembly, the piston is checked for free movement. The unit armorer replaces safety wire. The gunner cleans the rest of the weapon as follows:

(1) Cleans the bore using CLP and a bore brush attached to a cleaning rod. Does not reverse the direction of the bore brush while in the bore.

(a) Runs the brush through the bore several times until most of the powder fouling and other foreign matter have been removed.

(b) Swabs the bore several times using a cleaning rod and a swab wet with CLP.

(c) Swabs the bore several times using a cleaning rod and dry swab.

(2) Cleans the chamber using CLP and a chamber brush attached to a cleaning rod.

(a) Runs the brush through the chamber several times until most of the powder fouling and other foreign matter have been removed.

(b) Swabs the chamber several times using a cleaning rod and a swab wet with CLP.

(c) Swabs the chamber several times using a cleaning rod and dry swab.

(3) Cleans the receiver using a receiver brush and CLP.

(a) Brushes the receiver until most of the powder fouling and other foreign matter have been removed.

(b) Swabs the receiver several times using a cleaning rod section and a swab wet with CLP.

(c) Swabs the receiver several times using a cleaning rod section and dry swab.

(4) Wipes all the parts of the weapon except those that are rubber coated, using a rag wet with CLP.

(5) Dries completely all parts cleaned with CLP.

(6) Lubricates the following moving parts with CLP as instructed:

(a) Barrel Assembly. Lubricates on the camming surfaces of the bolt-locking lugs.

(b) Operating Rod Assembly. Lubricates on the rollers and those surfaces immediately below the yoke that ride within the receiver rails.

(c) Cover assembly. Lubricates inside the feed cam assembly.

(d) Bolt assembly. Lubricates on the bolt locking lugs and cam actuator roller, and in the camming recess (for the operating rod).

b. After lubricating, the components are cycled by hand to spread the CLP. Weapons fired infrequently or stored for prolonged periods should have a light film of CLP applied to the interior of the gas cylinder and the gas piston immediately after cleaning or inspection. Preventive maintenance is performed every 90 days, unless inspection reveals more frequent servicing is necessary. The use of the lubricant does not eliminate the requirement for cleaning and inspecting to ensure that corrosion has not formed. Before the weapon is used, the gas system and components must be clean and free of oil and lubricants.

c. All exposed surfaces of the M122 tripod, pintle assembly, and T&E mechanism are wiped down with a clean rag. For stubborn areas with hard-to-remove dirt, a steel brush or bore brush is used to loosen the particles. Then a clean rag is used to wipe them down and CLP is used to lubricate them.

d. The following procedures apply to cleaning and lubricating the M60 during unusual conditions:

After cleaning, lubricating, and inspecting the weapon, the gunner reassembles it in the reverse order of disassembly.

CAUTION

Be careful not to damage the internal ribs when installing the forearm assembly.

a. Replacing Receiver Assembly and Forearm Assembly. To replace the forearm assembly, the gunner slides it onto the receiver. He presses in on the bottom of forearm assembly to latch. He shakes the forearm assembly up and down to ensure it is seated.

b. Replacing the Trigger Mechanism Grip Assembly. To replace the trigger mechanism grip assembly, the gunner positions it on the bottom of the receiver, aligns it with the T-slot, and installs the front pin from the left side. He slides the slotted end of the flat leaf spring on the front pin. (The hooked end of the flat leaf spring should bend outward.) He pushes down and slides the hooked end of the flat leaf spring onto the grooved pin (Figure 2-15).

Figure 2-15. Replacing the trigger mechanism grip assembly.

c. Replacing the Barrel Assembly. To replace the barrel assembly, the gunner ensures that the barrel lock is up (unlocked) before inserting the barrel in the forearm assembly. He pushes the barrel lock down to lock it. Then, he lifts it up by the bipod and shakes it to ensure it is seated.

d. Replacing the Cover, Hanger and Cartridge Feed Tray Assembly. The gunner positions the hanger and cartridge feed tray assembly on the receiver. He installs the torsion spring and cover assembly and makes sure the ends of the torsion spring stick in the holes of the cover and receiver. (The hinge pin is inserted from right to left.) The gunner applies slight pressure to line up the torsion spring and inserts the cover hinge pin. He installs the hinge pin latch through the hinge pin until it locks. He keeps the cover assembly open until the machine gun is assembled.

e. Replacing the Bolt Assembly, Operating Rod Assembly, and Buffer Assembly. The gunner places the yoke of the operating rod assembly against the spool of the firing pin in the slot of the bolt assembly (Figure 2-16). Then, he pushes the spool forward. He seats the yoke between the spools of the firing pin and lets the yoke slide back in the bolt assembly.

(1) Slides the operating rod assembly with the bolt assembly into the weapon. Turns the bolt assembly so that the stripping lugs line up with the upper rails. Pushes in until the stripping lugs engage the rails.

(2) Turns the roller straight up and pushes the bolt assembly and operating rod assembly as a unit into the weapon.

(3) Pulls and holds the trigger while pushing the bolt assembly into the receiver until it locks in place.

(4) Installs the drive spring and guide assembly in the rear of the receiver.

(5) Inserts the buffer assembly against the end of the guide assembly and pushes until the groove on the buffer assembly lines up with the slot for buffer retaining yoke. Inserts the buffer retaining yoke.

f. Replacing the Stock. The gunner positions the stock on the rear of the receiver and pushes until it snaps in place. He pulls the cocking handle to the rear to lock the bolt assembly to the rear, and then he places the safety on "S." He closes the cover. While holding the charging handle, he pulls the trigger and eases the charging handle forward.

This section discusses the operation of the M60 machine gun. This includes loading, firing, unloading, cycle of functioning, adjustment of the sight, using both the bipod and tripod, and use of the M60 on a vehicular mount.

The M60 machine gun is loaded, fired, unloaded, and cleared from the open-bolt position. The safety lever must be in the "F" position before the bolt can be pulled to the rear. Before use belted ammunition must be linked with the double link at the open end of the bandoleer. It must be free of dirt and corrosion.

The gunner makes sure the weapon is cleared as previously described. He places the safety lever on "F". With his palm up, he pulls the cocking handle to the rear, then pushes it forward until it locks. With the bolt held to the rear, he places the safety lever on "S" and manually returns the cocking handle to the forward position. He turns the latch lever and opens the cover. He raises the cartridge feed tray and places the bandoleer on the bandoleer hanger. He places the first round of the belt in the feed groove with the double link first and the open side of the links down. He ensures that the round remains in the feed groove and holds the belt up (about six rounds from the loading end) while closing the cover (Figure 2-17).

The gunner unloads the M60 by pulling and locking the bolt to the rear position. He places the safety lever on "S", raises the cover and tray, and removes any ammunition or links from the tray. He performs the four-point safety check (see Section II).

The M60 gunners can recognize and correct stoppages when they know how the weapon functions. The weapon functions automatically as long as ammunition is fed into it and the trigger is held to the rear. Each time a round is fired, the parts of the weapon function in a cycle or sequence. Many of the actions occur at the same time. These actions are separated in this manual only for instructional purposes.

a. The first round of the belt is placed in the tray groove to start the cycle. Then, the trigger is pulled, releasing the sear from the sear notch. The rear of the sear is lowered and disengaged from the sear notch when the trigger is pulled to the rear. This procedure allows the operating rod and bolt to be driven forward by the expansion of the operating rod spring. The cycle stops when the trigger is released and the sear again engages the sear notch on the operating rod.

b. The sequence of functioning is as follows:

(1) Feeding. As the bolt starts its forward movement, the feed cam is forced to the right causing the feed cam lever to turn in the opposite direction and forcing the belt feed pawl over the next round in the bolt. The next round is then ready to be placed into the tray groove when the rearward action occurs again. As the bolt moves to the rear after firing, the cam roller forces the feed cam to the left. The feed cam lever is forced to turn, which moves the feed pawl to the right and places a round in the tray groove.

(2) Chambering. As the bolt travels forward, the upper locking lug engages the rim of the round. The pressure of the front and rear cartridge guides holds the round so that positive contact is made with the upper locking lug of the bolt. The front cartridge guide prevents forward movement of the link as the round is stripped from the belt. The upper locking lug carries the round forward. The chambering ramp causes the nose of the round to be cammed downward into the chamber. When the round is fully seated in the chamber, the extractor snaps over the rim of the round, and the ejector on the rail inside the receiver is depressed.

(3) Locking. As the round is chambered, the bolt enters the barrel socket. The upper and lower locking lugs contact the bolt camming surfaces inside the barrel and start turning the bolt clockwise. The action of the operating rod yoke against the bolt camming slot as the operating rod continues forward turns the bolt, completing its 90-degree (one-quarter turn) clockwise rotation. Locking is now complete.

(4) Firing. After the bolt is fully forward and locked, the operating rod continues to go forward, independent of the bolt, for a short distance. The yoke, engaged between the firing pin spools, carries the firing pin through the face of the bolt. The firing pin strikes the primer of the round and the primer fires the round.

(5) Unlocking. After the round is fired and the bullet passes the gas port, part of the expanding gases go into the gas regulator through the gas plug. The rapidly expanding gases enter the hollow gas piston, forcing the piston to the rear. As the operating rod continues to the rear, the operating rod yoke acts against the bolt camming slot. This causes the bolt to begin its counterclockwise rotation. The upper and lower locking lugs of the bolt contact the bolt camming surfaces inside the barrel socket and, as the bolt continues toward the rear, it completes a one-quarter turn counterclockwise. The rotation and movement to the rear unlocks the bolt from the barrel socket. Unlocking begins as the yoke of the operating rod contacts the curve of the bolt camming slot and ends as the bolt clears the end of the barrel socket.

(6) Extracting. Extracting begins during the unlocking cycle. The rotation of the bolt loosens the cartridge case in the chamber. As the piston and bolt move to the rear, the extractor pulls the cartridge case from the chamber.

(7) Ejecting. As the cartridge case is pulled from the chamber, the bolt passes by the ejector. This procedure causes the ejector clip to expand, forcing the ejector to push the expended cartridge. The extractor grips the right side of the cartridge and causes it to spin from the weapon as it reaches the ejection port. The empty belt links are forced out the link ejection port as the rearward movement of the bolt causes the next round to be positioned in the tray groove.

(8) Cocking. As the expanding gases force the gas piston to the rear, the operating rod first moves independently of the bolt. The yoke of the operating rod acts against the rear firing pin spool, pulling the firing pin from the primer of the spent cartridge case. The action of the piston assembly, continuing to the rear with the firing pin, releases the compression of the firing pin spring. As long as the trigger is held to the rear, the M60 continues to complete the eight steps of functioning automatically. When the trigger is released and the sear engages the sear notch, the cycle of functioning is stopped and the weapon is cocked. To prevent undue wear to the sear and sear notch, the gunner must hold the trigger firmly to the rear during firing.

The range scale on the rear sight is marked for each 100 meters from 300 to 1,100 meters. It can be adjusted for zeroing. Range changes are made by using either the scale retaining/adjusting screw or elevation knob. The scale retaining/adjusting screw is used to make major adjustments in elevation. The elevation knob is used to make minor adjustments, such as during zeroing (Figure 2-18). Four clicks on the elevation knob are equal to a 1-cm change in elevation or point of aim 1 cm. From the rear of the weapon, the elevation knob is turned clockwise to raise the rear sight and lower the strike of the round. It is turned counterclockwise to lower the sight and raise the strike of the round. The rear sight is adjustable for windage, 5 mils right or left of the zero index line. The windage knob is on the left side of the rear sight. One click on the windage knob equals a 1-cm change in deflection or point of aim 1 cm. The windage knob is turned toward the muzzle of the weapon to move the sight and the strike of the round to the right. It is turned toward the rear to move the sight and the strike of the round to the left.

a. Elevation. Before making elevation adjustments, the range knob must be at its highest setting. If the center of the shot group is above or below the aiming point, the gunner rotates the elevation knob by moving the rear sight slide in the direction of the desired change. One 180-degree turn in either direction moves the strike of the round 1/4 cm at 10 meters, or four clicks equals 1-cm change.

b. Windage. If the center of the group is to the left or right of the black aiming paster, the gunner must correct for windage. To correct windage, he rotates the windage knob to move in the direction of the desired change. For example, he rotates the windage knob toward the muzzle (counterclockwise) to move the strike of the round to the right; he rotates the windage knob toward the buttstock [clockwise] to move the strike of the round to the left. One click in either direction moves the strike of the round 1/2 cm at 10 meters.

c. 10-Meter Zeroing, Set the Sights (Mechanical Zero). The gunner indexes or places the range scale on a range of 500 meters. He aligns the windage by placing zero windage on the index line. He assumes a prone position and sights on the target.

The M122 tripod provides a stable mount for the M60, and it permits a high degree of accuracy and control. The tripod is recommended for marksmanship training and defensive employment.

a. Mounting M60 on the Tripod. The tripod assembly provides a stable and relatively lightweight base that is far superior to the bipod. The tripod may be extended and collapsed without difficulty. It consists of a tripod head, one front leg and two rear legs, and traversing bar. The traversing bar connects the two rear legs. It is hinged on one side with a sleeve and sleeve latch on the other, which allows the tripod to collapse to a closed position for carrying or storage or to lock in an open extended position for use. The traversing bar also supports the T&E mechanism. Engraved on the bar is a scale that measures direction in mils. It is graduated in 5-mil increments. It is numbered every 100 to 425 mils right of center and numbered every 100 to 450 mils left of center.

(1) The T&E mechanism is to provide controlled manipulation and the ability to engage predetermined targets.

(a) The traversing portion of the mechanism consists of the traversing handwheel and traversing slide-lock lever. As the traversing handwheel is turned, the muzzle of the weapon turns to the left or right, depending on the direction it is turned. Each click of the traversing handwheel indicates a 1-mil change in direction of the muzzle: 1 click equals 1 mil. The total of 100 mils traverse includes 50 mils right and 50 mils left of center.

(b) The elevating portion of the mechanism consists only of the elevating handwheel. The elevating handwheel has a mil-click device built into it (1 click = 1 mil). Engraved into the handwheel is a scale divided into 5-mil divisions and 1-mil subdivisions, for a total of 50-mil increments. There are 200 mils above and 200 mils below the zero mark, for a total of 400 mils in elevation change. Elevation readings are taken in two parts. First, the major reading is taken from the elevation screw plate. The second, minor reading is taken from the handwheel. The two readings are separated by a slash (/) when they are recorded.

(c) The traversing slide-lock lever allows rapid lateral adjustments along the traversing bar. Direction readings are taken from the scale on the traversing bar, using the left side of the traversing slide as an index. The direction of the reading comes from the position of the muzzle, not the position of the slide.

(2) To set up the tripod, the gunner unfolds the front leg and spreads the rear legs until the leg lock engages. He inserts the pintle assembly and rotates the pintle lock release cam to lock (Figure 2-19).

Figure 2-19. M122 tripod.

(3) To mount the M60, the gunner places the ends of the M60's front mounting pin on top of the pintle assembly. He presses the bottom of the latch to open the pintle assembly. The ends of the M60 mounting pin should lock in place on the pintle assembly (Figure 2-20).

Figure 2-20. Mounting of the M60 on the tripod.

(4) To attach the T&E mechanism to the weapon mounted on the tripod (Figure 2-21), the gunner centers the elevating and traversing handwheels. To do this, he turns the traversing handwheel toward his body as far as it will go, then turns it away two complete revolutions. He checks the traversing handwheel scale to ensure the "0" on the scale is aligned with the "0" index line before and after the two revolutions. At night, the gunner positions the traversing mechanism by turning the traversing handwheel toward his body as far as it will go, turns it away 50 clicks (two revolutions), and then allows the weapon to go forward.

(a) With the slide lock lever to the rear and the traversing handwheel to the left, the gunner places the mounting plate recess on the rear of the mounting plate. He pulls down the locating pin release and pushes the adapter assembly forward. (The locating pin automatically locks into position in the bottom of the mounting plate.)

(b) The gunner lowers the rear of the weapon, places the traversing slide on the traversing bar with the locking lever to the rear, and locks it into position. He indexes the left edge of the slide lock at zero.

Figure 2-21. Attachment of the T&E mechanism.

b. Dismounting M60 From the M122 Tripod. The gunner dismounts the M60 from the tripod by first removing the T&E mechanism. He releases the lock lever and raises the rear of the weapon. He grasps the carrying handle with his left hand and depresses the pintle latch with his right hand. He lifts the weapon from the pintle assembly.

The bipod assembly is used to fire from the prone position. The shoulder rest on the buttstock provides support for the weapon when fired in the bipod mode. The bipod group is held in place between the front sight and flash suppressor.

a. To lower a bipod leg, the gunner pulls it to the rear (compressing the lock spring) and rotates it downward (Figure 2-22). The leg automatically locks when in the down position. To return the legs up, the gunner pulls down on the legs and rotates upward.

Figure 2-22. Lowering of the bipod.

b. To extend a bipod leg, the gunner pulls down on the foot. The bipod leg plunger engages a notch in the bipod leg extension and holds it in the desired position. To shorten the bipod leg, the gunner depresses the bipod leg plunger and pushes up on the bipod foot (Figure 2-23).

The standard vehicular mount for the M60 machine gun is the M4 pedestal mount used on the HMMWV. One component of the pedestal mount, the M142 machine-gun mount, (which serves as a cradle for the weapon), is also adaptable to other vehicles (Figure 2-24).

a. To mount the weapon, the gunner locks the platform in the horizontal position by inserting the travel-lock pin into the travel lock. He places the front mounting pin (in the forearm assembly) into the front mounting lug. He lowers the receiver so that the rear locating pin snaps into the platform latch.

b. To dismount the weapon, the gunner ensures that the travel lock is engaged (holding the platform in a horizontal position). He grasps the carrying handle with one hand and depresses the platform latch with the other. He raises the rear of the weapon slightly and lifts it from the mount.

The M122 tripod provides a stable mount for the M60, and it permits a high degree of accuracy and control. The gunner unfolds the front leg, positions it toward the target, then spreads the rear legs until the leg lock engages.

A malfunction occurs when a mechanical failure causes the weapon to fire improperly. Neither defective ammunition nor improper operation by the gunner is considered a malfunction. If cleaning and lubricating the weapon does not fix the problem, then the gunner turns it in to the unit armorer. Table 2-3 shows malfunctions, their probable causes, and the corrective actions.

A stoppage is any interruption in the cycle of functioning caused by faulty action of the weapon or faulty ammunition. Stoppages are classified by their relationship to the cycle of functioning. Table 2-4 shows types of interruptions or stoppages, their probable causes, and the corrective actions.

IF NOTHING IS EJECTED AND THE WEAPON IS HOT (200 OR MORE ROUNDS FIRED IN LESS THAN 2 MINUTES), DO NOT OPEN THE COVER. MOVE THE SAFETY TO "S", WHICH PLACES THE WEAPON ON "S". KEEP THE WEAPON POINTED DOWNRANGE AND KEEP AWAY FROM THE WEAPON FOR 15 MINUTES, THEN CLEAR THE WEAPON.

BE CAREFUL IN CLEARING THE WEAPON WHEN THE BARREL IS HOT, A ROUND MAY FIRE (COOK OFF) DUE TO THE BARREL'S HEAT INSTEAD OF DUE TO THE FIRING MECHANISM. DURING TRAINING OR ON A FIRING RANGE, AFTER THE WEAPON HAS FIRED 200 ROUNDS, ITS BARREL IS CONSIDERED A HOT BARREL.

DURING COMBAT, WAIT 5 SECONDS, BECAUSE OF THE POSSIBILITY OF A "HANGFIRE," BEFORE APPLYING IMMEDIATE AND REMEDIAL ACTION. DURING TRAINING, WAIT 15 MINUTES BEFORE CLEARING A HOT WEAPON AND APPLYING IMMEDIATE OR REMEDIAL ACTION.

NOTE:

When applying immediate or remedial action on a cold or hot gun, if any part of the round (ranging from the tip of the bullet to the rim) is in the chamber, the gunner removes the ammunition from the feed tray only, then closes the cover and attempts to fire. If the weapon fires, he reloads and continues firing. If it does not fire, he clears the weapon (removes the round using a clearing rod with the cover closed, not using anything other than a clearing rod), then he inspects the weapon and ammunition.

Immediate action is action taken to reduce a stoppage without looking for the cause. Immediate action should be taken in the event of either a misfire or a cookoff. A misfire is the failure of a chambered round to fire. Such failure can be due to an ammunition defect or faulty firing mechanism. A cookoff is the firing of a round caused by the heat of a hot barrel and not by the firing mechanism. A cookoff can be avoided by applying immediate action within 10 seconds after a failure to fire. If the M60 stops firing, the gunner performs the following immediate actions. An effective memory aid is POPP, which stands for Pull, Observe, Push, and Press:

a. Pulls and locks the cocking handle to the rear while observing the ejection port to see if a cartridge case, belt link, or round is ejected. Ensures that the bolt remains to the rear to prevent double feeding if a round or cartridge case is not ejected.

b. If a cartridge case, belt link, or a round is ejected, returns the cocking handle to the forward position, aims on the target, and presses the trigger. If the weapon still does not fire, takes remedial action. If a cartridge case, belt link, or round is not ejected, takes remedial action.

Remedial action is any action taken to determine the cause of a stoppage and to restore the weapon to an operational condition. This action is taken only after immediate action fails to remedy the problem.

a. Cold Weapon Procedures. When a stoppage occurs with a cold weapon and immediate action has failed, the gunner uses the following procedures:

(1) Pulls the cocking handle to the rear, locking the bolt. Moves the safety to "S" and returns the cocking handle.

(2) Places the weapon on the ground or away from his face, opens the cover, and performs the four-point safety check. Reloads and continues to fire.

(3) If the weapon does not fire, clears the weapon and inspects it and the ammunition.

b. Hot Weapon Procedures. If the stoppage occurs with a hot weapon (200 rounds or more fired in 2 minutes or noted as previously for training), the gunner moves the safety to "S", waits 5 seconds (during training, lets the weapon cool for 15 minutes), then uses the same procedures as outlined for cold weapon procedures.

c. Jammed Cocking Handle. If a stoppage occurs and the cocking handle cannot be pulled to the rear by hand (the bolt may be fully forward and locked or only partially forward), the gunner takes the following steps:

(1) Tries once again to pull the cocking handle by hand.

CAUTION

Do not try to force the cocking handle to the rear with your foot or a heavy object. This could damage the weapon.

(2) If the weapon is hot enough to cause a cookoff, moves all soldiers a safe distance from the weapon and keeps them away for 15 minutes.

(3) After the gun has cooled, opens the cover and disassembles the gun. Ensures rearward pressure is kept on the cocking handle until the buffer is removed. (The assistant gunner helps the gunner do this.)

Destruction of any military weapon is only authorized as a last resort to prevent enemy capture or use. This paragraph discusses the field-expedient means of this destruction; it does not replace published policies. In combat situations, the commander has the authority to destroy weapons, but he must report this destruction through channels.

a. Disassemble the weapon as completely as time permits. Use the barrel or tripod mount to destroy the bolt, buffer, and operating rod group, barrels, rear and front sights, and mounts.

b. Bury the disassembled weapon or dump the parts into a stream, a sump, or a latrine.

c. Burn the weapon by placing an incendiary grenade on the receiver group over the bolt (with the cover resting on the grenade) and detonating the grenade.